This invention relates to night vision equipment. More particularly, it relates to an image intensifier for night vision equipment.
Modern image intensifiers typically use phosphor outputs that present bright green images to the viewer. These images can be emerald green to various shades of lime green in color, depending upon the phosphor that is used.
The human eye is most sensitive to the color greenxe2x80x94which makes it easy to view the green light phosphor outputs from intensified images. Likewise, the emissions of green light from phosphor outputs are easy to see by others who are using image intensification or night vision equipment.
If one individual is using the typical green light image intensifier in connection with operating a weapon site, or in another night vision application, the green image produced by the intensifier optics is reflected directly back and shines on the operator""s eye and face. It is not unusual for a large portion of the reflection to cover an area around and outside the user""s eye. During a combat situation, the reflection can appear as a bright spot to an opposing party who is also using night vision equipment. Not only does it create a point of detection, but the point also becomes a target point.
To minimize the above problem, rubber eyecups are used to shield green light reflections from image intensifiers. Nevertheless, there is generally some noticeable light leakage, particularly when large biocular eyepieces or eyepieces with long eye relief are used.
The device described here prohibits or greatly reduces the emission from the phosphorus screen of an image intensifier. It allows the user of night vision equipment to remain undetected when the opposing side is also using long range night vision equipment.
The invention is an improved filter for use in an image intensifier for night vision equipment. The filter is dichroic. It is positioned between the user""s eye and the output of an image intensifier tube. The filter permits transmission of light that is substantially in the wave length blue and effectively blocks most of the green wave length as well as other wave lengths. While blue light can be viewed by the person using the image intensifier, it is not highly visible to others using night vision equipment. Therefore, the dichroic filter minimizes or eliminates the targeting spot created by conventional image intensifiers.
The invention is described in greater detail below.